ABSTRACT
Pneumococcal surface protein A (PspA) is an important virulence factor of Streptococcus pneumoniae. PspA exists as two major families, which include variable but serologically cross-reactive proteins. Previous studies with a family 1 PspA antigen suggested that children develop low concentrations of anti-PspA after pneumococcal carriage or infection. In this study, antibody to PspA families 1 and 2 was measured by an enzyme immunoassay of the serum and saliva of children with a history of culture-proven pneumococcal colonization and/or acute otitis media and in the serum and saliva of adults. The PspA families of the pneumococcal strains isolated from children were determined. The majority of the children had high serum and salivary anti-PspA concentrations to the PspA family they had encountered and low concentrations to the other, whereas adults had high antibody concentrations to both PspA families, both in serum and in saliva. The results suggest that children have a relatively family-specific antibody response to the PspA family they have been exposed to and that any PspA vaccine for children should contain members of both major PspA families.
Subject(s)
Antibodies, Bacterial/analysis , Antibodies, Bacterial/blood , Bacterial Proteins/immunology , Pneumococcal Infections/immunology , Saliva/immunology , Streptococcus pneumoniae/immunology , Adult , Carrier State/immunology , Child, Preschool , Family Health , Humans , Immunoenzyme Techniques/methods , Immunoglobulin A/analysis , Immunoglobulin A/blood , Immunoglobulin G/analysis , Immunoglobulin G/blood , Infant , Otitis Media/immunology , Otitis Media/microbiology , Streptococcus pneumoniae/isolation & purificationABSTRACT
Bacterial culture of middle-ear fluid (MEF), the standard for etiologic diagnosis of acute otitis media (AOM), has revealed Streptococcus pneumoniae (Pnc) to be a major pathogen responsible for one-third of AOM cases. In the present study, we compared the results of polymerase chain reaction (PCR) based on the amplification of the pneumolysin gene with the results of pneumococcal culture, for 2595 MEF samples obtained during AOM events in 831 children who were followed from 2-24 months of age in the Finnish Otitis Media Vaccine Trial. PCR results were positive for 47.1% of the MEF samples, and culture results were positive for 27.3% of the samples. PCR-positive, culture-negative samples were associated with previous Pnc AOM in a time-dependent pattern, concurrent antibiotic treatment, low volume of MEF, and concurrent nasopharyngeal carriage. PCR-positive AOM represented a clinically less severe disease, compared with culture-positive Pnc AOM. A positive PCR result seemed to indicate the presence of viable, although often nonculturable, Pnc.